A conventional display device may include an LCD, an LED, a PDP, and an OLED. The display device can display texts and images by driving liquid crystal, plasma, LED, neon, light source and so on. For example, an LCD is a widely used display screen such as expressway traffic information displays, weather forecasting displays, police information displays, advertisement or amusement displays placed in downtown, as they need a reduced voltage, consume less energy, have a good performance, emit a relatively high light intensity, and have a uniform lighting surface and a wide range of view. However, as they have a great dispersion angle and a lighting area, they need a lot of LCDs or some great power LCDs, which consume a substantial amount of energy.
Chinese utility model application No. 200620013306.1 with patent publication No. CN 2094180Y discloses an electronic information display screen, for solving the problem of substantial energy consumption. The application is incorporated herein by reference.
As shown in FIGS. 1A and 1B, the display screen comprises a screen 1 comprising an array 2 of LEDs 3 and a controller.
As shown in FIG. 1B, each of the LEDs 3 of the array 2 is disposed to face a concave mirror 4 so that the concave mirror 4 can focus the light emitted from the LED and the focused light can reach far efficiently. It needs less LEDs and a less amount of energy for a good display.
Chinese invention-patent application No. 02142477.2 with patent publication No. CN 1226658C discloses a LCD display device. The application is incorporated herein by reference.
FIG. 2A shows a conventional LCD screen 20 comprising a light emitting array 21, a light guide 22 placed before the light emitting array 21, a first polarizer 23 placed before the light guide 22, an LCD panel 24 placed before the first polarizer 23, and a second polarizer 25 provided before the LCD panel 24.
FIG. 2B shows the light emitting array of the screen in FIG. 2A, and FIG. 2C shows the light guide of the screen in FIG. 2A. As shown in FIGS. 2B and 2C, the light emitting array 21 comprises an individual light source 211 including three light emitting elements of red, blue and green primary colors. Only one of the three primary color light emitting elements is turned on at a time, or all of them are turned on or each of them turned off simultaneously, or any two of them are turned on simultaneously, thereby operating in eight different lighting manners or arrangements for a color display as desired. The primary color light emitting elements comprise LEDs or OLEDs. A controller is used for controlling the display color and the light intensity.
The above-mentioned conventional light emitting display screens can be used for advertisement display placed outdoors or indoors. But they consume electric power, especially a substantial power when used outdoors. In addition, the display screens glint and cause a light pollution of the denizens in the neighborhoods. When used in expressways, the glinting affects drivers' sight, which could tend to cause accidents.